1. Field of the Invention
The present invention relates to a method of manufacturing an organic light emitting device, and more particularly, to a method of manufacturing an organic light emitting device by using a laser induced thermal imaging (LITI) method.
2. Description of the Related Art
An organic light emitting display device, which is a flat panel display device, includes an anode, a cathode, and an intermediate layer including at least an organic emission layer interposed between the anode and the cathode. The organic light emitting display device is a self-emissive display device, has a wide viewing angle, high contrast ratio, and high response speed, and thus is considered to be a next-generation display device. The organic light emitting display device may further include at least one organic layer in addition to a hole injecting layer (HIL), a hole transporting layer (HTL), an electron transporting layer (ETL), and an electron injecting layer (EIL) besides the organic emission layer, depending on whether the organic emission layer is formed of a polymer organic material or a small-molecule organic material.
In order for the organic light emitting display device to achieve full color images, an organic layer needs to be patterned. Examples of the patterning method include a shadow mask method for small-molecule organic light emitting display devices, and an ink-jet printing method or a laser induced thermal imaging (LITI) method for polymer organic light emitting display devices. The LITI method converts laser light into thermal energy, transfers a transfer layer onto a substrate of an organic light emitting display device by using the converted thermal energy, and forms red (R), green (G), and blue (B) organic layers. The LITI method is capable of minutely patterning an organic layer, may be used on a large surface, and is advantageous in achieving a high resolution.
FIGS. 1A and 1B are schematic cross-sectional views for explaining a conventional LITI method. Referring to FIG. 1A, the LITI method prepares an acceptor substrate 40 including a pixel electrode 43 and a pixel definition layer 45 formed on an upper portion of a substrate 41.
Thereafter, a donor film 30 is laminated on an upper portion of the acceptor substrate 40. The donor film 30 includes a base film 31, a light to heat conversion (LTHC) layer 33, and a transfer layer 35.
A laser beam emitted from a light source 10 is irradiated onto the acceptor substrate 40 through a patterned mask 20. The laser beam is absorbed into the LTHC layer 33 of the donor film 30, is converted into thermal energy, and thus the donor film 30 expands according to a shape of the mask 20. In this regard, referring to FIG. 1B, a rectangular opening portion is used as the mask 20 which is patterned so as to correspond to a pixel region, so that an intensity of energy irradiated onto an edge of a pixel is relatively lower than that of the energy irradiated onto a center of the pixel. Thus, thermal conductivity is highest in a center of the donor film 30 and is rapidly lowered the closer to an edge of the donor film 30 that contacts the acceptor substrate 40. This results in the weakness of transferring a transfer layer onto the pixel edge, which deteriorates performance of a device.